Answer:
Height of wall is 12 ft.
Explanation:
In the shown figure, AB denotes the height of the wall, BC denotes the distance between foot of the ladder and wall and AC denotes the length of the ladder.
Let h be the height of wall. By Pythagoras Theorem,
(AB)² + (BC)² = (AC)²
According to the problem, AC = 13 ft, AB = h ft and BC = (h - 7) ft:
h² + (h-7)² = (13)²
h² + h² + 49 - 14h = 169
2h² - 14h - 120 = 0
h² - 7h - 60 = 0
By mid-term splitting,
h² - 12h + 5h - 120 = 0
h(h - 12) + 5(h - 12) = 0
(h - 12) x (h + 5) = 0
h = 12 ft or h = -5 ft
Since, height of wall cannot be negative. Hence, the height of wall is 12 ft.
